MHA(Master HA)是一款开源的MySQL的高可用程序，它为MySQL主从复制架构提供了automating master failover功能。MHA在监控到master节点故障时，会提升其中拥有的最新数据的slave节点成为新的master节点，在此期间，MHA会通过其它从节点获取额外信息来避免一致性方面的问题。MHA还提供了master节点的在线切换功能，即按需切换master/slave节点。
MHA服务有两种角色，MHA Manager(管理节点)和MHA Node(数据节点)：
MHA Manager：通常单独部署在一台独立机器上管理多个master/slave集群，每个master/slave集群称为一个application； MHA node：运行在每台MySQL服务器上，它通过监控具备解析和清理log功能的脚本来加快故障转移
Manager节点：
-masterha_check_ssh：MHA依赖的SSH环境检测工具； -masterha_check_repl:MySQL复制环境检测工具； -masterha_manager:MHA服务主程序； -masterha_check_status:MHA运行状态探测工具； -masterha_master_monitor：MySQL master节点可用性检测工具； -masterha_master_switch:master节点切换工具； -masterha_conf_host:添加或删除配置的节点； -masterha_stop：关闭MHA服务的工具；
Node节点：
-save_binary_logs：保存和复制master的二进制日志； -apply_diff_relay_logs:识别差异的中继日志事件并用于其他slave； -fiter_mysqlbinlog：去除不必要的ROLLBACK事件(MHA已不再使用这个工具)； -purge_relay_logs：清除中继日志(不会阻塞SQL线程)；
自定义扩展：
-secondary_check_script：通过多条网络路由检测master的可用性； -master_ip_failover_script:更新appliction使用的masterip； -shutdown_script:强制关闭master节点； -report_script:发送报告； -init_conf_load_script：加载初始配置参数； -master_ip_online_change_script:更新master节点ip地址
实验拓扑：
node1:192.168.150.137 MHA manager node2:192.168.150.138 MHA node mariadb master node3:192.168.150.139 MHA node mariadb slave candidate node4:192.168.150.140 MHA node mariadb slave
配置过程：
1、修改每台服务器的hosts文件 /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.150.137 node1.com node1 192.168.150.138 node2.com node2 192.168.150.139 node3.com node3 192.168.150.140 node4.com node4 2、node2-node4进行mariadb的yum安装 yum -y install mariadb-server 3、配置ssh互信通信环境 [root@node1 ~]# ssh-keygen -t rsa -P ‘‘ Generating public/private rsa key pair. Enter file in which to save the key (/root/.ssh/id_rsa): Created directory ‘/root/.ssh‘. Your identification has been saved in /root/.ssh/id_rsa. Your public key has been saved in /root/.ssh/id_rsa.pub. The key fingerprint is: a2:f2:10:28:cd:ea:7b:d8:f4:95:15:6e:73:a6:9d:4e root@node1.com The key‘s randomart image is: +--[ RSA 2048]----+ | | | . | | . . | | + = o | |o + . S * . | |.. o . + . E | |. * o . o | |.. * . . | | oo . | +-----------------+ [root@node1 ~]# ls .ssh/id_rsa id_rsa id_rsa.pub [root@node1 ~]# cat .ssh/id_rsa.pub > .ssh/authorized_keys [root@node1 ~]# ssh node1 The authenticity of host ‘node1 (192.168.150.137)‘ can‘t be established. ECDSA key fingerprint is 2a:e3:03:52:8c:84:02:59:a2:26:a3:b2:f6:74:6c:3c. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added ‘node1,192.168.150.137‘ (ECDSA) to the list of known hosts. Last login: Wed Mar 29 15:06:52 2017 from 192.168.150.1 [root@node1 ~]# ll .ssh/authorized_keys -rw-r--r-- 1 root root 396 3月 29 15:35 .ssh/authorized_keys [root@node1 ~]# chmod go= .ssh/authorized_keys [root@node1 ~]# scp -p .ssh/id_rsa .ssh/authorized_keys node2:/root/.ssh root@node2‘s password: id_rsa 100% 1675 1.6KB/s 00:00 authorized_keys 100% 396 0.4KB/s 00:00 [root@node1 ~]# scp -p .ssh/id_rsa .ssh/authorized_keys node3:/root/.ssh The authenticity of host ‘node3 (192.168.150.139)‘ can‘t be established. ECDSA key fingerprint is 2a:e3:03:52:8c:84:02:59:a2:26:a3:b2:f6:74:6c:3c. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added ‘node3,192.168.150.139‘ (ECDSA) to the list of known hosts. root@node3‘s password: id_rsa 100% 1675 1.6KB/s 00:00 authorized_keys 100% 396 0.4KB/s 00:00 [root@node1 ~]# scp -p .ssh/id_rsa .ssh/authorized_keys node4:/root/.ssh root@node4‘s password: Permission denied, please try again. root@node4‘s password: id_rsa 100% 1675 1.6KB/s 00:00 authorized_keys 100% 396 0.4KB/s 00:00 [root@node1 ~]# ssh node2 Last login: Wed Mar 29 15:07:05 2017 from 192.168.150.1 [root@node2 ~]# exit 登出 Connection to node2 closed. [root@node1 ~]# ssh node3 Last login: Wed Mar 29 15:07:18 2017 from 192.168.150.1 [root@node3 ~]# exit 登出 Connection to node3 closed. [root@node1 ~]# ssh node3 Last login: Wed Mar 29 15:40:05 2017 from node1.com [root@node3 ~]# exit 登出 Connection to node3 closed. [root@node1 ~]# ssh node4 Last failed login: Wed Mar 29 15:39:53 CST 2017 from node1.com on ssh:notty There was 1 failed login attempt since the last successful login. Last login: Wed Mar 29 15:39:30 2017 from node1.com [root@node4 ~]# exit 登出 Connection to node4 closed. [root@node1 ~]# ssh node4 Last login: Wed Mar 29 15:40:13 2017 from node1.com [root@node4 ~]# exit 登出 Connection to node4 closed. 4、修改mysql参数 master： [mysqld] innodb_file_per_table = 1 skip_name_resolve = 1 log-bin = master-bin relay-log = relay-bin server_id = 1 slave： [mysqld] innode_file_per_table = 1 skip_name_resolve = 1 log-bin = master-bin relay-log = relay-bin server_id = 2 read_only = 1 relay_log_purge = 0 5、主库开启并创建授权账号 master: MariaDB [(none)]> SHOW MASTER STATUS; +-------------------+----------+--------------+------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +-------------------+----------+--------------+------------------+ | master-bin.000003 | 245 | | | +-------------------+----------+--------------+------------------+ 1 row in set (0.00 sec) MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO ‘repluser‘@‘192.168.%.%‘ IDENTIFIED BY ‘replpass‘; MariaDB [(none)]> GRANT ALL ON *.* TO ‘mhauser‘@‘192.168.%.%‘ IDENTIFIED BY ‘mhapass‘; #此为mha的管理账号 MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘read_only‘; #此时主库是可写可读 +---------------+-------+ | Variable_name | Value | +---------------+-------+ | read_only | OFF | +---------------+-------+ 1 row in set (0.00 sec) 6、从库进行主从功能开启 node3、node4操作相同 [root@node3 ~]# mysql Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 2 Server version: 5.5.52-MariaDB MariaDB Server Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others. Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement. MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST=‘192.168.150.138‘,MASTER_USER=‘repluser‘,MSTER_PASSWORD=‘replpass‘,MASTER_LOG_FILE=‘master-bin.000003‘,MASTER_LOG_POS=245; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Master_Host: 192.168.150.138 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000003 Read_Master_Log_Pos: 245 Relay_Log_File: relay-bin.000001 Relay_Log_Pos: 4 Relay_Master_Log_File: master-bin.000003 Slave_IO_Running: No Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 245 Relay_Log_Space: 245 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULL Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 0 1 row in set (0.00 sec) MariaDB [(none)]> START SLAVE; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.150.138 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000003 Read_Master_Log_Pos: 497 Relay_Log_File: relay-bin.000002 Relay_Log_Pos: 782 Relay_Master_Log_File: master-bin.000003 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 497 Relay_Log_Space: 1070 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 1 1 row in set (0.00 sec) MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘read_only‘; #此时从库是只读模式 +---------------+-------+ | Variable_name | Value | +---------------+-------+ | read_only | ON | +---------------+-------+ 1 row in set (0.00 sec) 7、此时一主两从架构已经配置完成，安装MHA包 manager节点(node1)： 安装mha4mysql-manager-0.56-0.el6.noarch.rpm和mha4mysql-node-0.56-0.el6.noarch.rpm yum install mha4mysql* -y node节点(node2-node4): 安装mha4mysql-node-0.56-0.el6.noarch.rpm yum -y iinstall mha4mysql-node-0.56-0.el6.noarch.rpm 8、初始化MHA 创建配置目录及配置文件(在node1上执行) [root@node1 ~]# mkdir /etc/masterha [root@node1 ~]# vim /etc/masterha/app1.cnf [server default] user=mhauser password=mhapass manager_workdir=/data/masterha/app1 master_log=/data/masterha/app1/manager.log remote_workdir=/data/masterha/app1 ssh_user=root repl_user=repluser repl_password=replpass ping_interval=1 [server1] hostname=192.168.150.138 candidate_master=1 [server2] hostname=192.168.150.139 candidate_master=1 [server3] hostname=192.168.150.140 9、启动前检测 ssh互信配置是否OK [root@node1 ~]# masterha_check_ssh --conf=/etc/masterha/app1.cnf ...... Warning: Permanently added ‘192.168.150.139‘ (ECDSA) to the list of known hosts. Wed Mar 29 17:03:03 2017 - [debug] ok. Wed Mar 29 17:03:03 2017 - [info] All SSH connection tests passed successfully. mysql复制集群的连接配置是否OK [root@node1 ~]# masterha_check_repl --conf=/etc/masterha/app1.cnf ...... Wed Mar 29 17:04:40 2017 - [info] 192.168.150.138(192.168.150.138:3306) (current master) +--192.168.150.139(192.168.150.139:3306) +--192.168.150.140(192.168.150.140:3306) Wed Mar 29 17:04:40 2017 - [info] Checking replication health on 192.168.150.139.. Wed Mar 29 17:04:40 2017 - [info] ok. Wed Mar 29 17:04:40 2017 - [info] Checking replication health on 192.168.150.140.. Wed Mar 29 17:04:40 2017 - [info] ok. Wed Mar 29 17:04:40 2017 - [warning] master_ip_failover_script is not defined. Wed Mar 29 17:04:40 2017 - [warning] shutdown_script is not defined. Wed Mar 29 17:04:40 2017 - [info] Got exit code 0 (Not master dead). MySQL Replication Health is OK. 10、启动MHA [root@node1 ~]# nohup masterha_manager --conf=/etc/masterha/app1.cnf > /data/masterha/app1/manager.log 2>& 1 &[1] 16989 [root@node1 ~]# tail -f /data/masterha/app1/manager.log 192.168.150.138(192.168.150.138:3306) (current master) +--192.168.150.139(192.168.150.139:3306) +--192.168.150.140(192.168.150.140:3306) Wed Mar 29 21:51:58 2017 - [warning] master_ip_failover_script is not defined. Wed Mar 29 21:51:58 2017 - [warning] shutdown_script is not defined. Wed Mar 29 21:51:58 2017 - [info] Set master ping interval 1 seconds. Wed Mar 29 21:51:58 2017 - [warning] secondary_check_script is not defined. It is highly recommended setti ng it to check master reachability from two or more routes.Wed Mar 29 21:51:58 2017 - [info] Starting ping health check on 192.168.150.138(192.168.150.138:3306).. Wed Mar 29 21:51:58 2017 - [info] Ping(SELECT) succeeded, waiting until MySQL doesn‘t respond.. 11、启动后查看master节点状态 [root@node1 ~]# masterha_check_status --conf=/etc/masterha/app1.cnf app1 (pid:16623) is running(0:PING_OK), master:192.168.150.138 12、进行故障转移测试 (1)maser节点关闭mariadb [root@node2 ~]# killall mysqld mysqld_safe (2)此时在manager上可以看到转移的日志 ----- Failover Report ----- app1: MySQL Master failover 192.168.150.138(192.168.150.138:3306) to 192.168.150.139(192.168.150.139:3306) succeeded Master 192.168.150.138(192.168.150.138:3306) is down! Check MHA Manager logs at node1.com:/data/masterha/app1/manager.log for details. Started automated(non-interactive) failover. The latest slave 192.168.150.139(192.168.150.139:3306) has all relay logs for recovery. Selected 192.168.150.139(192.168.150.139:3306) as a new master. 192.168.150.139(192.168.150.139:3306): OK: Applying all logs succeeded. 192.168.150.140(192.168.150.140:3306): This host has the latest relay log events. Generating relay diff files from the latest slave succeeded. 192.168.150.140(192.168.150.140:3306): OK: Applying all logs succeeded. Slave started, replicating from 19 2.168.150.139(192.168.150.139:3306)192.168.150.139(192.168.150.139:3306): Resetting slave info succeeded. Master failover to 192.168.150.139(192.168.150.139:3306) completed successfully. 故障转移后，manager会自动停止，此时查看master状态 [root@node1 ~]# masterha_check_status --conf=/etc/masterha/app1.cnf app1 is stopped(2:NOT_RUNNING). (3)查看其它两个库状态 node3 已成功接管master，并可读写 MariaDB [(none)]> SHOW MASTER STATUS; +-------------------+----------+--------------+------------------+ | File | Position | Binlog_Do_DB | Binlog_Ignore_DB | +-------------------+----------+--------------+------------------+ | master-bin.000003 | 245 | | | +-------------------+----------+--------------+------------------+ 1 row in set (0.00 sec) MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘read_only‘; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | read_only | OFF | +---------------+-------+ 1 row in set (0.00 sec) node4 MariaDB [(none)]> SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.150.139 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000003 Read_Master_Log_Pos: 245 Relay_Log_File: relay-bin.000002 Relay_Log_Pos: 530 Relay_Master_Log_File: master-bin.000003 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 245 Relay_Log_Space: 818 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 2 1 row in set (0.00 sec) MariaDB [(none)]> SHOW GLOBAL VARIABLES LIKE ‘read_only‘; +---------------+-------+ | Variable_name | Value | +---------------+-------+ | read_only | ON | +---------------+-------+ 1 row in set (0.00 sec) (4)提供新的从节点已修复复制集群 master界定啊故障后，需要重新准备好一个新的MySQL节点。基于来自于master节点的备份恢复后，将其重新配置为mster的从节点即可。新加入节点IP为原master节点IP，否则还得修改appl.cnf中相应的设置，最后再次启动manager，并再次检查状态。 [root@node2 ~]# rm -rf /var/lib/mysql/* [root@node2 ~]# vim /etc/my.cnf 添加从库两选项 read_only = 1 relay_log_purge = 0 [root@node2 ~]# systemctl start mariadb.service [root@node2 ~]# mysql Welcome to the MariaDB monitor. Commands end with ; or \g. Your MariaDB connection id is 2 Server version: 5.5.52-MariaDB MariaDB Server Copyright (c) 2000, 2016, Oracle, MariaDB Corporation Ab and others. Type ‘help;‘ or ‘\h‘ for help. Type ‘\c‘ to clear the current input statement. MariaDB [(none)]> GRANT REPLICATION SLAVE,REPLICATION CLIENT ON *.* TO ‘repluser‘@‘192.168.%.%‘ IDENTIFIED BY ‘replpass‘;Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> GRANT ALL ON *.* TO ‘mhauser‘@‘192.168.%.%‘ IDENTIFIED BY ‘mhapass‘; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> FLUSH PRIVILEGES; Query OK, 0 rows affected (0.00 sec) MariaDB [(none)]> CHANGE MASTER TO MASTER_HOST=‘192.168.150.139‘,MASTER_USER=‘repluser‘,MASTER_PASSWORD=‘r eplpass‘,MASTER_LOG_FILE=‘master-bin.000003‘,MASTER_LOG_POS=245; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> SHOW SLAVE\G ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MariaD B server version for the right syntax to use near ‘‘ at line 1MariaDB [(none)]> START SLAVE; Query OK, 0 rows affected (0.01 sec) MariaDB [(none)]> SHOW SLAVE STATUS\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.150.139 Master_User: repluser Master_Port: 3306 Connect_Retry: 60 Master_Log_File: master-bin.000003 Read_Master_Log_Pos: 245 Relay_Log_File: relay-bin.000002 Relay_Log_Pos: 530 Relay_Master_Log_File: master-bin.000003 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 245 Relay_Log_Space: 818 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0 Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: Replicate_Ignore_Server_Ids: Master_Server_Id: 2 1 row in set (0.00 sec) 再次开启manager查看状态，状态全部OK，主库变更为node3 [root@node1 ~]# nohup masterha_manager --conf=/etc/masterha/app1.cnf > /data/masterha/app1/manager.log 2>&1 & [root@node1 ~]# masterha_check_status --conf=/etc/masterha/app1.cnf app1 (pid:17229) is running(0:PING_OK), master:192.168.150.139
提供额外机制，防止对master的监控做出误判、VIP添加、在进行故障转移时对原有master节点执行STONITH操作避免脑裂，可通过shutdown_scrip实现、必要时，进行在线master节点转换；
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原文地址：http://voidyao000.blog.51cto.com/12458042/1911817
